Osteoporosis is a disease of bones that leads to an increased risk of bones fracture. Generally, osteoporosis implies a reduction of bone mineral density (BMD) and may lead to pathologic or fragility fractures. Previous fragility fractures indicate that there is a strong risk for future fragility fractures. In that an estimate of BMD and an assessment of the fracture risk may be crucial to prevent future bones fractures.
Bones are formed by two types of osseous tissue, i.e. compact tissue or cortical bone tissue and cancellous bone tissue.
Bone Mineral Density (BMD) is often determined by Radiogrammetry image processing of an x-ray image (DXR-BMD). Among the techniques used for measuring BMD, the determination of BMD based on digital x-ray radiogrammetry, resides in the evaluation of the thickness of the cortical bone tissue and the width of the bone of interest. Determining these parameters, from, for example, a digitized X-ray image acquired with the maximum resolution offered by today's standard medical X-ray machines is a difficult task.
U.S. Pat. No. 6,763,257 discloses a method for estimating BMD by the use of radiogrammetry. The BMD is calculated based on a functional relationship between thickness (T) of the cortical bone tissue and the width (W) of the bone of interest, according to a function having the following appearance:BMD=B×T×(1−T/W)
where B is determined from a calibration where pairs of (T, W) have been calibrated to corresponding BMD values for one or more bones.
Generally, this calibration may include the calibration for each type of image sources, e.g. for different model and types of X-ray detector system and different acquisition modalities. This calibration generates a B which can be used in the estimate of BMD based on image data collected through a specific protocol, e.g., exposure setting, such as focus distance, energy used, and post processing, such as edge enhancement.
However, in several situations, such as emergency situations, the specific protocol for acquiring radiograms cannot be followed, hampering the usability of DXR for the estimate of BMD.
Hence, an improved method for estimating BMD of a bone would be advantageous, and in particular a more efficient and/or reliable method for assessing the risk of bone fractures from image data collected in emergency situation would be advantageous.